The following prior art reflects the state of the art of which applicant is aware and is included herewith to discharge applicant's acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these references teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
______________________________________ U.S. Pat. No. ISSUE DATE INVENTOR ______________________________________ 2,649,133 August 18, 1953 Just 2,674,557 April 6, 1954 Boggs 2,964,065 December 13, 1960 Haroldson, et al. 3,125,478 March 17, 1964 Pratt 4,080,879 March 28, 1978 Hoden, et al. 4,273,601 June 16, 1981 Weingart 4,579,617 April 1, 1986 Oberg, et al. 4,923,541 May 8, 1990 Burger 5,024,712 June 18, 1991 Lecourt, et al. ______________________________________
The patent to Boggs (U.S. Pat. No. 2,674,557) teaches a process of making tubular structures out of a glass fibre mat impregnated with liquid thermosetting resinous material and winding the treated mat around a mandrel by means of an enveloping belt. The mandrel and belt operate in a heated oven to heat cure the resinous material.
The patent to Oberg, et al. (U.S. Pat. No. 4,579,617) teaches an apparatus and method for manufacturing cylindrical components such as tanks and pipes by winding layers of sheet material around a rotating mandrel. FIG. 3 shows a flat sheet (8) being softened by a heating source (9) so as to cause it to drop onto the rotating mandrel. Other layers are directly wound on the mandrel without being heat softened. The various layers are bonded to each other by an adhesive spray which is applied as the mandrel rotates.
The patent to Burger (U.S. Pat. No. 4,923,541) issued to applicant on May 8, 1990 teaches a method and apparatus for manufacturing composite tubes which disclose some concepts related to the present invention. The method in U.S. Pat. No. 4,923,541 employs an inflatable floating mandrel (21) caged in a frame (23). A conveyor sheet (22) is wrapped around the mandrel and composite sheet material placed on the conveyor is also wrapped around the mandrel. The various layers employed are coated with a resin. The mandrel with its partially formed tube is then removed from the cage and inserted into a hollow mold and expanded to shape the tube to the internal surface of the mold.
The apparatus and method of the instant invention differ in major respects over the patented devices as will be described in the descriptive portions of the specification.
The other prior art listed above but not specifically described further catalog the prior art of which the applicant is aware. These references diverge even more starkly from the references specifically distinguished above.